1. Field of the Invention
The present invention pertains to a diaphragm for a beam of electromagnetic radiation and its use in a device for the collimation of this beam.
It can be applied especially in the medical field, to X-ray imaging devices.
2. Description of the Prior Art
At present, diaphragms or irises of collimation devices for electromagnetic radiation are made according to the principle of the photographic camera diaphragm where the beam-limiting agent is arranged in hinged plates which are moved to define a more or less disk-shaped zone for the passage of the beam. The shape of these plates is very precise and depends on the variation desired in the cross-section of the passage. Consequently, when there is a wide range of variations in the cross-section, large rigid plates are used and the equipment is very bulky. The corollary of this geometric constraint is that it is difficult to obtain small cross-sections. Furthermore, the mechanical tolerances have to remain very low.
These difficulties have led to the envisaging of fluid-displacement diaphragms for high energy beams, the said diaphragms comprising, for example, a matrix of channels, perpendicular to the beams, which are filled independently of one another. However, these diaphragms have the disadvantage of requiring complicated means to control the movement of the fluid in each channel. The object of the invention is to remove the above disadvantages.